[Bug libstdc++/69266] bootstrap failure undefined reference to `std::basic_ios<char, std::char_traits<char> >::

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69266

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Nothing has changed here, so I don't know why it would start failing on Cygwin.